Damping of a microelectromechanical oscillator in turbulent superfluid He4 : A probe of quantized vorticity in the ultralow temperature regime

We report a comprehensive investigation of the effects of quantum turbulence and quantized vorticity in superfluid $⁴\mathrm{He}$ on the motion of a microelectromechanical systems (MEMS) resonator. We find that the MEMS is uniquely sensitive to quantum turbulence present in the fluid. To generate turbulence in the fluid, a quartz tuning fork (TF) is placed in proximity to the MEMS and driven at a large amplitude. We observe that at low velocity, the MEMS is damped by the turbulence, and that above a critical velocity, ${v}_c\ensuremath{\simeq}5\phantom{\rule{4pt}{0ex}}\mathrm{mm}\phantom{\rule{0.28em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$, the turbulent damping is greatly reduced. We find that above ${v}_c$, the damping of the MEMS is reduced further for increasing velocity, indicating a velocity dependent coupling between the surface of the MEMS and the quantized vortices constituting the turbulence. We propose a model of the interaction between vortices in the fluid and the surface of the MEMS. The sensitivity of these devices to a small number of vortices and the almost unlimited customization of MEMS open the door to a more complete understanding of the interaction between quantized vortices and oscillating structures, which in turn provides a new route for the investigation of the dynamics of single vortices.